Recently, saving of paper resources is a part of the global environmental protection. Regarding saving and reuse of paper resources through image forming apparatuses, the effective use of the rear face of a piece of paper having a front face printed is generally accepted in the society. Moreover, it is general that used paper is collected as a material of paper, and is used again as recycled paper.
According to the reuse of paper having one face printed, however, the number of reuse is limited to one time. Moreover, when the used paper is reused as a material, collection itself needs an effort and a cost, and processing of the material also needs an effort.
Hence, various schemes have been proposed which make the paper reusable in multiple times in an office. In order to reuse paper on which an image is once formed by a toner image as a paper resource, there is an idea of physically eliminating or optically achromatizing the image formed on the paper formed by the toner in order to make the paper reusable.
Regarding physical elimination of the image in order to make the paper reusable, there are a technique of applying a processing liquid that eliminates the toner on the image-formed face of the paper and of heating it in order to dissolve the toner, thereby eliminating the image, and a technique of sanding the image-formed face of the paper in order to scrape the toner image. However, those techniques need a time and an effort, and the paper to be reused is often damaged.
There is also a technique of using a thermo-sensitive achromatic agent and of causing a heating-oven-type achromatic apparatus to perform achromatizing. Moreover, there is known a technique of eliminating an achromatic toner using partial optical energy. When those achromatic apparatuses are installed in an office, however, the achromatic apparatus in addition to a printing apparatus like a printer needs additional power, and additional installation space, so that it is not economical.
Moreover, most achromatic apparatuses need much time for achromatizing, which are not user-friendly to users, and are not convenient thereto. In consideration of such a problem, it is desirable that the achromatic apparatus should be built in another device like a printer, and such another device should be capable of printing using an achromatic toner and of achromatizing thereof in addition to a normal printing.
Unexamined Japanese Patent Application KOKAI Publication No. H08-152823 discloses an image forming apparatus that has a function of performing printing on recording paper through development, transferring and fixing with an achromatic toner, and a function of emitting light for achromatizing to characters and images of the achromatic toner printed on the recording paper and of performing achromatizing.
In addition, various examples of achromatic toner and achromatic apparatus are proposed and Unexamined Japanese Patent Application KOKAI Publication No. H05-204278 discloses an apparatus which heats a toner image with a sensitizing colorant that can be achromatized by infrared ray and a boron-based compound, and which performs achromatizing with infrared, thereby remarkably improving the achromatizing speed.
According to this apparatus, effective light sources as the achromatic light source are halogen, flash, and LED (Light Emitting Diode) lamps, and in particular, examples using the halogen lamp are mainly disclosed. The halogen lamp is also used as a heat source since it emits energy in the long-wavelength range which is typical of far-infrared ray. As far as the heat-source is concerned, it is disclosed that the heat source is effective for the purpose of assisting an achromatic reaction.
Moreover, Unexamined Japanese Patent Application KOKAI Publication No. H07-049634 discloses a configuration in which a fixing device at the time of image formation and an achromatic device for achromatizing are common devices, a thermal roller pair of the fixing device at the time of image formation is also used as a heating unit at the time of achromatizing, and a light source for emitting achromatic light is arranged at the downstream side of the thermal roller pair in the fixing device based on the technology that the achromatic action becomes effective if a toner image is heated in advance and is irradiated with achromatic light in order to achromatize the toner image.
According to the related art disclosed in Unexamined Japanese Patent Application KOKAI Publication No. H08-152823, the effectiveness of the printer is demonstrated which has an achromatic device and a printing device integrated together and which performs achromatizing and printing through the same device. In this case, however, it is desirable to reduce the total power consumption including the power consumption by an achromatic unit in addition to the power consumption by the printer main body. The issue of power consumption is not disclosed in Unexamined Japanese Patent Application KOKAI Publication No. H08-152823.
Moreover, according to the related art disclosed in Unexamined Japanese Patent Application KOKAI Publication No. H07-049634, the halogen lamp emits light including not only near-infrared ray but also rays in the ultraviolet range, the visible light range, and from near-infrared range to far-infrared range. Hence, energies with not only absorption wavelength of the sensitizing colorant but also other excessive wavelengths which do not contribute to an achromatic reaction are emitted, so that it is not an economical energy source.
Unexamined Japanese Patent Application KOKAI Publication No. H07-049634 discloses the effectiveness of light emission with a resin being heated to a temperature equal to or higher than the glass transition temperature Tg, but in the case of heating using the halogen lamp, when the lamp is installed linearly relative to the paper passing through the convey path, the filament of the halogen lamp needs to increase the length thereof, and the power consumption becomes large inevitably, so that is is not always a good scheme from the standpoint of power consumption.
Furthermore, when the halogen lamp is used, such a lamp is always turned on at the time of achromatizing. Since the lamp itself is a consumable item which is broken down for several thousand hours, the running cost becomes large.
Regarding the light source other than the halogen lamp, an LED, etc., as an example light source is disclosed, but there is no disclosure about the setting of the light source under a specific achromatic condition. Moreover, regarding the combination of such light source with the achromatic toner, there is no proposal for a more effective optical energy, so that a relationship between appropriate light and an effective achromatic action of the colorant is still unclear.
In the case of a combination in which two devices: an LED lamp; and a heating device are combined together, there is an unignorable problem that is heat loss due to convection, irradiation, and thermal conduction by the heating device. However, the achromatic apparatus disclosed in Unexamined Japanese Patent Application KOKAI Publication No. H05-204278 and having both infrared ray generating device and heating device combined together is not configured in consideration of the heat-loss problem due to convection, irradiation and thermal conduction by the heating device. Accordingly, a task of reducing power consumption originating from such heat loss, etc., is not disclosed or suggested in Unexamined Japanese Patent Application KOKAI Publication No. H05-204278.
Conversely, as explained above, Unexamined Japanese Patent Application KOKAI Publication No. H07-049634 discloses the effectiveness of light emission with the resin being heated to a temperature equal to or higher than the glass transition temperature Tg. In order to increase the temperature of the toner to, for example, around 140 degrees Celsius which is higher than the glass transition temperature Tg, it is effective for achromatizing the toner image if the paper is irradiated with achromatic light when the temperature of the paper surface is substantially 200 degrees Celsius. However, if the paper is heated to the temperature of substantially 200 degrees Celsius for a long time, the paper may change the color thereof.
In this case, it is possible to achromatize the toner image while suppressing the color-change of the paper in accordance with the setting, such as the convey speed of the paper and the heating range, but a failure, such as paper jamming, turning off of the device power source, or a false operation of the switch may occur.
When such a failure occurs and the paper stopping at the heating unit in the achromatizing operation is left for a certain time, the paper changes the color thereof, which possesses a risk of smoking.
Hence, when a failure that the paper is stopping at the heating unit occurs, it is necessary to immediately terminate heating of the paper, and in general, a heater that is the heat source is turned off.
However, in order to set the surface temperature of the paper being conveyed to substantially 200 degrees Celsius, the temperature of the heater is set to be a further higher temperature. Accordingly, even if the heater is turned off, the temperature of radiation heat does not immediately decrease, in fact, the surface temperature of the paper increases and the color change of the paper advances.
When the failure is paper jamming, the jammed paper partially rises, and may be located closely to or contact the heat radiation surface of the heater. In this case, it easily brings about smoking from the paper.